1) SLAs are almost always customer initiated (see "Customer Must Request Financial Credit." in https://cloud.google.com/appengine/sla for example)

2) The SLA isn't tied to the status page at all, a customer can request an SLA refund for any reason provided they have proof of damages.

TL;DR: status pages are a helpful tool to let folks know something's wrong and that the team isn't asleep at the wheel, not a legally binding contract.